.\"Copyright 2010 (c) EPFL
.TH RTF_CREATE_FIR_LOWPASS 3 2010 "EPFL" "rtfilter library"
.SH NAME
rtf_create_fir_lowpass, rtf_create_fir_highpass, rtf_create_fir_bandpass
- Creates FIR lowpass, highpass and bandpass windowed sinc filters
.SH SYNOPSIS
.LP
.B #include <rtf_common.h>
.sp
.BI "hfilter rtf_create_fir_lowpass(unsigned int " nch ", int " proctype ","
.br
.BI "                               double " fc ", unsigned int " hlen ","
.br
.BI "                               KernelWindow " wndtype ");"
.br
.BI "hfilter rtf_create_fir_highpass(unsigned int " nch ", int " proctype ","
.br
.BI "                               double " fc ", unsigned int " hlen ","
.br
.BI "                               KernelWindow " wndtype ");"
.br
.BI "hfilter rtf_create_fir_bandpass(unsigned int " nchann ", int " proctype ","
.br
.BI "                                double " fc_low ", double " fc_high ","
.br
.BI "                                unsigned int " hlen ","
.br
.BI "                                KernelWindow " wndtype ");"
.br
.SH DESCRIPTION
.LP
\fBrtf_create_fir_lowpass\fP() creates a lowpass windowed sinc filter
processing \fInchann\fP channels of data type specified by \fIproctype\fP
with \fIfc\fP as normalized cutoff frequency and \fIhlen\fP as the half
length of the window.
.LP
\fBrtf_create_fir_highpass\fP() is the same as
\fBrtf_create_fir_lowpass\fP() but creates a highpass filter.
.LP
\fBrtf_create_fir_bandpass\fP() is the same but creates a bandpass filter
with \fIfc_low\fP and \fIfc_high\fP as respectively the lowpass and highpass
normalized cutoff frequencies.
.LP
A normalized frequency is the ratio between the absolute frequency and the
sampling frequency (i.e. a value of 1.0 refers to the sampling frequency).
.LP
The parameter \fIproctype\fP has the same meaning as in \fBrtf_create_filter\fP(3). Refers to its manpage for more details.
.LP
The parameter \fIwndtype\fP specifies the type of window applied to the
impulse response and can take the following values: \fBBLACKMAN_WINDOW\fP, \fBHAMMING_WINDOW\fP or \fBRECT_WINDOW\fP (see a book on signal
processing for details about their meaning).
.SH "RETURN VALUE"
.LP
Returns the handle to the created filter in case of success, NULL otherwise.
.SH "SEE ALSO"
.BR rtf_create_filter (3),
.BR rtf_destroy_filter (3)